Re: [PATCH v22 12/13] arm64: dts: qcom: Add psci reboot-modes for monaco boards

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] System hang on reboot when requesting vendor-specific reboot modes on unsupported firmware
--

commit da9bb648c6683dbd4e4976f8d350b0b7213b92be
Author: Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>

arm64: dts: qcom: Add psci reboot-modes for monaco boards

This commit adds PSCI SYSTEM_RESET2 reboot-modes for monaco-evk and
qcs8300-ride to support bootloader and emergency download (edl) reboot modes.

> diff --git a/arch/arm64/boot/dts/qcom/monaco-evk.dts b/arch/arm64/boot/dts/qcom/monaco-evk.dts
> index 9d17ef7d2caf1..df668dbf2bc60 100644
> --- a/arch/arm64/boot/dts/qcom/monaco-evk.dts
> +++ b/arch/arm64/boot/dts/qcom/monaco-evk.dts

[ ... ]

> @@ -661,6 +661,13 @@ usb2_id: usb2-id-state {
>  	};
>  };
>  
> +&psci {
> +	reboot-mode {
> +		mode-bootloader = <0x80010001 0x2>;
> +		mode-edl = <0x80000000 0x1>;
> +	};
> +};

Could adding these modes introduce a regression on boards running older
firmware where a system hang occurs on reboot?

The commit message notes that support for these modes is firmware dependent.
However, if a user requests a bootloader reboot on a system where the
firmware lacks SYSTEM_RESET2 support, it appears the system might hang
instead of falling back to a normal reboot.

If psci-reboot-mode registers these modes unconditionally,
psci_reboot_mode_write() sets the reset command to the vendor-specific
value.

During reboot, psci_sys_reset() calls psci_handle_reset_cmd(). If
psci_system_reset2_supported is false and the vendor reset type is non-zero,
it returns without making a PSCI call.

This causes psci_sys_reset() to return NOTIFY_DONE. The kernel then reaches
the end of the restart chain and spins indefinitely with a failure panic.

Should the psci-reboot-mode driver or the PSCI reset handler be updated to
handle unsupported firmware before introducing these device tree properties?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260514-arm-psci-system_reset2-vendor-reboots-v22-0-28a5bde07483@oss.qualcomm.com?part=12